21207172 has 24 divisors (see below), whose sum is σ = 42840000. Its totient is φ = 8997600.

The previous prime is 21207167. The next prime is 21207223. The reversal of 21207172 is 27170212.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 922 + ... + 6577.

It is an arithmetic number, because the mean of its divisors is an integer number (1785000).

Almost surely, 2^21207172 is an apocalyptic number.

It is an amenable number.

21207172 is an abundant number, since it is smaller than the sum of its proper divisors (21632828).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21207172 is a wasteful number, since it uses less digits than its factorization.

21207172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7611 (or 7609 counting only the distinct ones).

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 21207172 is about 4605.1245368611. The cubic root of 21207172 is about 276.7967073071.

Adding to 21207172 its reverse (27170212), we get a palindrome (48377384).

The spelling of 21207172 in words is "twenty-one million, two hundred seven thousand, one hundred seventy-two".